NZ's 'Mount Doom' at risk of eruption

A New Zealand volcano that featured as Mount Doom in the Lord Of The Rings trilogy is in danger of erupting.

Officials say Mount Ruapehu, New Zealand's largest active volcano, is experiencing a build-up of pressure in a subterranean vent.

New Zealand's department of conservation (DOC) has warned hikers to avoid the summit, saying temperature readings by scientists indicate there is an increased risk of eruption.

"The current situation can't continue. Ruapehu is so active that the temperatures have been going up and down a lot," DOC volcanic risk manager Harry Keys told Radio New Zealand.

"They generally haven't gone up as we've expected for some weeks now, and sooner or later that situation will be rectified, either in a small, relatively passive way, or with a significant eruption."

Official monitoring body GNS Science says the temperature a few hundred metres below a lake in the crater of the North Island mountain is estimated to be 800 degrees Celsius, but the temperature at the lake itself is just 20 degrees.

It said this indicated a vent was partially blocked, leading to increased pressure that made eruptions more likely "over the next weeks to months".

The 2,797-metre mountain last erupted in 2007, sending a lahar - a fast-moving stream of mud and debris - down the mountain, but causing no injuries.

In 1953, a massive lahar from the mountain caused New Zealand's worst rail disaster when it washed away a bridge at Tangiwai and a passenger train plunged into the Whangaehu River, claiming 151 lives.

Director Peter Jackson used Mount Ruapehu and the neighbouring Mount Ngauruhoe to depict Mount Doom in the Lord Of The Rings movies.

Another nearby volcano, Mount Tongariro, erupted in August, sending a plume of ash 6,100 metres into the atmosphere, showering the North Island and disrupting domestic air travel.